diff --git a/bsim/spin_stroboscope/spin_stroboscope.f90 b/bsim/spin_stroboscope/spin_stroboscope.f90
index 55e0e67ca..73c8640c5 100644
--- a/bsim/spin_stroboscope/spin_stroboscope.f90
+++ b/bsim/spin_stroboscope/spin_stroboscope.f90
@@ -242,7 +242,7 @@ program spin_stroboscope
   orbit(0) = start_orb
 
   do i = 1, 3
-    mode_is_oscillating(i) = (delta(2*i-1) /= 0 .and. delta(2*i) /= 0)
+    mode_is_oscillating(i) = (delta(2*i-1) /= 0 .or. delta(2*i) /= 0)
   enddo
   if (.not. rf_on) mode_is_oscillating(3) = .false.